Recording and reproduction of magnetic recording apparatus for the audio, the video recorder and the computer are generally performed by sliding a magnetic head and a magnetic medium, e.g., a magnetic tape, with keeping them in contact each other. At this time, reproduction output lowers if the scratched powders of the magnetic tape and the dusts in the peripheral of the recording apparatus are adhered to the surface of the magnetic head, and output cannot be obtained at all in the end. For recovering the reproduction output lowered in such a way, a cleaning medium, such as a cleaning tape, is used to restore the reproduction output by cleaning the stain adhered on the surface of the magnetic head.
On the other hand, magnetic recording becomes more and more higher density, and so it is difficult to accomplish satisfactory recording and reproduction if the tip of a magnetic head and a magnetic tape are not in contact well with each other. For maintaining good touch of a magnetic tape with a magnetic head, a cleaning tape is required not only to clean stain on a magnetic head but also to adjust the form of the head to a certain degree. In particular, a magnetic head of a magnetic recorder for high density recording of the shortest recording wavelength of 1 μm or less is used in recent years, and the gap length in this magnetic head is 0.4 μm or less, therefore a trace of stain on the head will interfere with recording and reproducing performance.
Further, ferrite having a high surface hardness has been mainly used as the material of a magnetic head, but a metal head such as Sendust has come into use for the advancement in high density. Since a metal head is soft as compared with a ferrite head and the abrasion of the head is large, it becomes important that the amount of head abrasion due to a cleaning tape is small.
Further, with the tendency of high density recording, an MR head (Magnetic Resistive Head) has come into use. The height of a shield type MR head element for general use is several micrometers or less, thus the amount of head abrasion of MR head has to be small as far as possible as compared with a ferrite head and a Sendust head.
Further, magnetic recorders capable of using both a metal vapor deposition tape (ME tape) and a metal powder tape (MP tape) such as Hi-8 and DVC have appeared on the market. With the vapor deposition tape, since a metal thin film having high stiffness is brought into contact with a magnetic head, it is difficult to obtain a good contact condition, i.e., recording and reproducing performance, if the tip of the magnetic head is not acute. In addition, since the vapor deposition tape does not contain an abrasive, magnetic head abrasion due to contact with the tape is little, so that the conformability to the magnetic head is low. On the other hand, since the magnetic layer of the metal tape contains a magnetic powder in a binder, the touch of the magnetic tape to the magnetic head is soft, thus the touch of the tape to the head is not so influenced according to the form of tip of the head, and the conformability to the magnetic head is good due to its abrading force.
Accordingly, when the metal tape is run to the magnetic head after the vapor deposition tape has been run, the touch of the tape to the head is not so influenced, contrary to this, when the vapor deposition tape is run after the metal tape has been run, there are cases where the touch of the tape to the head results in a disorder.
As the prior technique of the abrasive tape for abrading a magnetic head, e.g., an abrasive tape comprising a nonmagnetic support having provided thereon an intermediate layer containing a nonmagnetic powder and an abrasive layer containing a nonmagnetic abrasive laminated in this order from the support is disclosed in JP-A-62-92205 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). This abrasive tape takes two-layer constitution, and contrives to prevent scratches of a head from occurring while maintaining the abrasive force by making the surface of the intermediate layer coarse on the one hand and making the particle size of the abrasive particles in the upper abrasive layer fine on the other hand. However, this abrasive tape is for finishing abrasion of a magnetic head, a head is too much abraded as can be seen from its surface roughness of from 0.03 to 0.3 μm, and it is difficult to perform proper abrasion as cleaning, and so this tape is not suitable for a cleaning tape. Abrasive tapes similar to the above tape are disclosed in JP-A-62-94270 and JP-A-62-92205. These tapes also have an abrasive layer of two-layer constitution, but it is difficult to perform good cleaning without scratching a magnetic head by proper abrasion, therefore they are not suitable for a cleaning medium.
With respect to an MR head, as compared with a ferrite head and a metal head, e.g., a Sendust head, there is such a problem that head abrasion must be lessened as far as possible, and the effective means for solving this problem has been required.
As a cleaning tape for a magnetic head, a technique of two-layer constitution comprising a flexible support having provided thereon two cleaning layers, which Young's modulus of the upper cleaning layer is made larger than that of the lower cleaning layer which is compatible with good cleaning property and less head abrasion is disclosed in JP-A-6-139531. However, according to this technique, since both of two layers contain a ferromagnetic powder, the anisotropy of Young's modulus of the tape as a whole is conspicuously generated. Hence it is difficult to exhibit good cleaning property to each form when the forms of the magnetic head are different after a metal tape and a vapor deposition tape are used. In particular, the form of the tip of the head after cleaning is not acute, and so good touch of the vapor deposition tape to the head cannot be brought about, and the recovery of interchangeability of a metal tape and a vapor deposition tape is insufficient.
It has been found that, even if a magnetic head is different in forms, the touch of the vapor deposition tape to the head can be made good and the interchangeability of a metal tape and a vapor deposition tape can be sufficiently recovered if the stain on the magnetic head can be removed with a cleaning medium having proper flexibility and good surface property and, at the same time, if the form of the magnetic head can be adjusted.
Accordingly, in cleaning a magnetic head of a high density magnetic recording and reproducing apparatus, the present inventors provided a cleaning medium for a magnetic recording medium capable of sliding along with the contour of a head causing less head abrasion, capable of using in a metal head, capable of doing good cleaning irrespective of the form of a magnetic head, capable of adjusting the form of a magnetic head without scratching the tip of the head after cleaning, and having good interchangeability. This cleaning medium for a magnetic recording apparatus comprises a nonmagnetic support having provided thereon a lower coating layer mainly containing a nonmagnetic inorganic powder and a binder, and a cleaning layer containing at least a ferromagnetic inorganic powder and a binder provided on the lower coating layer, wherein the binder in the lower coating layer is a polyurethane resin which is a reaction product containing at least diol and organic diisocyanate as main starting materials, and the polyurethane resin contains short chain diol having a cyclic structure and long chain diol containing an ether group. However, the strength of the coated film was insufficient because the dispersibility of the nonmagnetic inorganic powder was not sufficient, and so cleaning effect was not satisfactory.